What is it like to be a PhD student at Uppsala University? In this new blog series we invite our students to tell us a little bit about their research and life as Biology PhD students.

In this first blog we hear from Matthew Bodle Cowen a fourth-year PhD student at the Department of Organismal Biology, Uppsala University. He is specializing in vertebrate palaeontology. His doctoral project explores the environments and ecosystems of the water-to-land transition.

The man who stares at fish

By Matthew Bodle Cowen

Reconstructing the distant past is like figuring out a jigsaw, except 90% of the pieces are missing, half of what you have left are ripped, and the picture can be only interpreted from faint chemical traces of the ink. Also, while you think you could find more pieces if you looked in the box, said box is up a mountain in Greenland and you don’t have funding to look for it.

I work on fish fossils from the early part of the Carboniferous, around 360 million years ago. Back then, a huge lake existed in Greenland, roughly 10 times the size of today’s lake Vänern. The lake is somewhat mysterious as, despite its vast size, we have relatively few fossils from it and they seem to represent only a handful of different taxa. How could such a vast lake have such little living in it?

We know that the lake existed during a mass extinction event known as the Hangenberg crisis. Fossils of deformed plant spores from the lake match with similar spores from other sites around the world. These spores seem to have been deformed by a burst of UV radiation, perhaps from a dying star going supernova. The fish in the lake, most commonly represented by a minnow-sized ray-finned fish called Cuneognathus, are the survivors of this event.

I’ve spent long enough looking at these specimens that they have their own names to me. 'The Rhino'.... 'Dragon-eyes'... 'Chappell'... "

A typical day for me begins with selecting specimens to work on. Each fossil has been given a label marking the year and place it was discovered, and a specimen number for reference, but I’ve spent long enough looking at these specimens that they have their own names to me. “The Rhino”, because of a protruding rostral bone. “Dragon-eyes”, because the ornamental dermal bone around the orbit looks like dragon scales. “Chappell”, because the specimen number, 2425020, puts that damn song in my head. No fish is exactly the same, but it’s striking the way they are almost all preserved in the same way. Each is on its side, flattened by the weight of the sediment that piled on top of it the second it hit the bottom. The bones of the skull are what interest me, and they too have been flattened in such a way that you can never see all of them on the same fish, but you might see all of them if you looked at enough fish. That’s my goal, to see every bone and construct a kind of platonic ideal Cuneognathus, against which I can make morphological comparisons. This will tell me what kind of fish I’m working with, and if there are any new species lurking in the dusty drawers of the collections.

Next begins the ritual of coating the specimens for photography. Beautiful as they are, the fossils are too shiny and too variable in colour to distinguish some features when seen in a photo. Hence, they must be coated to make them matte. I carry my specimens to the fume hood in the lab and begin assembling the spraying apparatus. This consists of a suggestive-looking piece of glassware containing a fine white powder that, when heated over a bunsen burner, forms a fine mist that can be sprayed onto the specimens. The powder is in fact the same ammonium chloride that coats the Saltlakrits so beloved in Sweden, and in thin layers its easy to imagine the pitch-black fossil bones are made of that confection. Exposed to too much airborne moisture, the powder will dissolve into hydrochloric acid and begin to wear my fossils just as too many godisar wears on the teeth, so I must work quickly and in a dry environment.

My samples freshly coated, I refill the tray and carry the specimens to the former “quiet office”, which houses the microscope I will need to examine them. The microscope shares the office with a post-doc and another PhD student. Both human occupants work on data obtained through high-powered synchrotron scanning, essentially a CT scan on steroids. The scans allow them to produce three-dimensional images of objects buried deep in rock, negating the need for the costly and time-devouring excavation of the sort most people think of paleontologists doing. Instead, my colleagues time is devoured segmenting- digitally picking out the fossil material from the rock in their scans. My colleagues are also working on material from Greenland, though from a different, older layer of rock to the one I work on. In their rocks they find the remains of strange, four-legged beasts- Tetrapods- the first vertebrates to set foot on the newly green land of Greenland.

I switch on the microscope and the computer attached to it, which will allow me to view my subjects on a bigger screen, and take the photos I will one day publish as evidence that I have, in fact, been doing something. Looking at the fish in front of me, I see that among the bones and scales of Cuneognathus I expect to be there are scattered pieces of another fish, an acanthodian. Ancanthodians were an ancestor of sharks and rays, but with pointy spines growing from their fins. I find these spines quite often, randomly lying in the rocks. I think of the sludgy bottom of a modern-day lake, with all bits and pieces of dead creatures lying in it. Will someone study them too, in 360 million years?

Photos taken, I clean the powder off the fossils and put them back in the drawers. I return to my own office, upload the pictures, make notes. I look through the literature on similar fish from the same era, compare with what I see in my material. Do my interpretations make sense? Did I see something new today? What should I keep in mind for tomorrow?

I know that my fossils are just a tiny part of the overall picture; a single pixel of a single piece of that vast puzzle of the past. But with each pixel revealed, the picture becomes just that little bit clearer.

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We would love to hear from other students. Please send me a message if you are interested in writing an entry for our blog (mario.vallejo-marin@ebc.uu.se)